NYU Observational Astronomy 2013-2014

Class II
- the scientific method
- earth's rotation and its origin and consequences

Transcript

1. lecture 2 the scientific method - earth’s motion observational astronomy 1
2. lecture 2 the scientific method - earth’s motion recap R.A. / Dec: tied to the object, never changes H.A. / Dec: tied to the observer/object Alt. / Az : tied to the observer Other systems: •Ecliptic •Galactic Other Concepts: •Ecliptic •Local Sidereal Time 2
3. lecture 2 the scientific method - earth’s motion recap R.A. / Dec: tied to the object, never changes H.A. / Dec: tied to the observer/object Alt. / Az : tied to the observer Other systems: •Ecliptic •Galactic Other Concepts: •Ecliptic •Local Sidereal Time NCP Celestial Equator NP SP Eq •Vernal Equinox R.A. Decl. SCP 3
4. lecture 2 the scientific method - earth’s motion recap R.A. / Dec: tied to the object, never changes H.A. / Dec: tied to the observer/object Alt. / Az : tied to the observer Other systems: •Ecliptic •Galactic zenith nadir C.E. NP SP Eq Horizon NORTH Alt. Other Concepts: •Ecliptic •Local Sidereal Time 4
5. lecture 2 the scientific method - earth’s motion goals: •familiarize with and orient yourself in the night sky •understand (and predict!) basic observable astronomy phenomena •understanding the scientific method 5
6. lecture 2 the scientific method - earth’s motion goals: •familiarize with and orient yourself in the night sky •understand (and predict!) basic observable astronomy phenomena •understanding the scientific method 6
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16. lecture 2 the scientific method - earth’s motion everyone was an astronomer Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry sky above me and the moral law within me. Aristotle 350 BC Plato 380 BC ... Kant 1755 16
17. lecture 2 the scientific method - earth’s motion everyone was an astronomer Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry sky above me and the moral law within me. Aristotle 350 BC Plato 380 BC ... Ptolemy 150 BC Copernicus 1500 Kepler 1600 Kant 1755 Galileo 1650 17
18. lecture 2 the scientific method - earth’s motion the earth is round, and it orbits around the sun 18
19. lecture 2 the scientific method - earth’s motion the earth is round, and it orbits around the sun the earth is round, and it orbits around the sun 19
20. lecture 2 the scientific method - earth’s motion http://en.wikipedia.org/wiki/File:Ptolemaicsystem-small.png Peter Apian, Cosmographia, Antwerp, 1524 from Edward Grant, "Celestial Orbs in the Latin Middle Ages", Isis, Vol. 78, No. 2. (Jun., 1987). Geocentric models are natural: from our perspective we see the Sun moving, while we stay still the earth is round, and it orbits around the sun 20
21. lecture 2 the scientific method - earth’s motion As observations improve this model cannot fit the data anymore! not easily anyways... http://en.wikipedia.org/wiki/File:Cassini_apparent.jpg Source Encyclopaedia Brittanica 1st Edition Author Dr Long's copy of Cassini, 1777 the earth is round, and it orbits around the sun 21
22. lecture 2 the scientific method - earth’s motion A new model fit the data “naturally” (for now anyways...) http://en.wikipedia.org/wiki/File:Copernican_heliocentrism_diagram-2.jpg Image of heliocentric model from Nicolaus Copernicus' "De revolutionibus orbium coelestium". the earth is round, and it orbits around the sun 22
23. lecture 2 the scientific method - earth’s motion A new model fit the data “naturally” (for now anyways...) Image of heliocentric model from Nicolaus Copernicus' "De revolutionibus orbium coelestium". http://en.wikipedia.org/wiki/File:Pluralitas.jpg Okham’s razor: "Pluralitas non est ponenda sine necessitate" John Duns Scotus (1265–1308) http://en.wikipedia.org/wiki/File:Copernican_heliocentrism_diagram-2.jpg the earth is round, and it orbits around the sun 23
24. lecture 2 the scientific method - earth’s motion prescription for a scientific theory: • favor the models that require fewer parameters 24
25. lecture 2 the scientific method - earth’s motion prescription for a scientific theory: • favor the models that require fewer parameters • a scientific theory must be provable 25
26. lecture 2 the scientific method - earth’s motion prescription for a scientific theory: • favor the models that require fewer parameters • a scientific theory must be provable falsifiable 26
27. lecture 2 the scientific method - earth’s motion everyone was an astronomer Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry sky above me and the moral law within me. Aristotle 350 BC Plato 380 BC ... Popper 1934 Ptolemy 150 BC Copernicus 1500 Kant 1755 Galileo 1650 Kepler 1600 The Logic of Scientific Discovery 27
28. lecture 2 the scientific method - earth’s motion prescription for a scientific theory: • favor the models that require fewer parameters • a scientific theory must be falsifiable • most scientific theories are actually based largely on probabilistic induction and modern inductive inference (Solomonoff, frequentist vs Bayesian methods...) 28
29. lecture 2 the scientific method - earth’s motion the earth is round, and it orbits around the sun Image of heliocentric model from Nicolaus Copernicus' "De revolutionibus orbium coelestium". http://en.wikipedia.org/wiki/File:Copernican_heliocentrism_diagram-2.jpg 29
30. lecture 2 the scientific method - earth’s motion earth’s motion 30
31. lecture 2 the scientific method - earth’s motion timelaps - 1 hour steps 31
32. lecture 2 the scientific method - earth’s motion timelaps - 1 hour steps 32
33. lecture 2 the scientific method - earth’s motion timelaps - 1 day steps 33
34. lecture 2 the scientific method - earth’s motion earth’s spin http://www.weatherscience.net/ 34
35. lecture 2 the scientific method - earth’s motion earth’s rotation www.bradfreese.com 35
36. lecture 2 the scientific method - earth’s motion ref: infinity imagined 36
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38. lecture 2 the scientific method - earth’s motion orbit of the earth I. sidereal time 38
39. lecture 2 the scientific method - earth’s motion orbit of the earth I. sidereal time 39
40. lecture 2 the scientific method - earth’s motion orbit of the earth solar day = 24h 40
41. lecture 2 the scientific method - earth’s motion sidereal day = 23h 56m orbit of the earth 41
42. lecture 2 the scientific method - earth’s motion sidereal day = 23h 56m orbit of the earth the RA transiting at a given standard time advances by about 4 minutes per day 4 min/day 2 hours/month 24 hours / 12 months 42
43. lecture 2 the scientific method - earth’s motion orbit of the earth LST: local sidereal time is the RA of the meridian at zenith in a given place at a given time 43
44. lecture 2 the scientific method - earth’s motion orbit of the earth LST = H.A. + RA LST: local sidereal time is the RA of the meridian at zenith in a given place at a given time 44
45. lecture 2 the scientific method - earth’s motion orbit of the earth LST = H.A. + RA LST: local sidereal time is the RA of the meridian at zenith in a given place at a given time ALSO LOOK UP: Universal time Local time Mean Solar time Greenwich time Daylight saving time... 45
46. lecture 2 the scientific method - earth’s motion orbit of the earth II. “the ever changing sky” 46
47. lecture 2 the scientific method - earth’s motion orbit of the earth 47
48. lecture 2 the scientific method - earth’s motion Stars in this direction visible at night orbit of the earth 48
49. lecture 2 the scientific method - earth’s motion six month later... orbit of the earth 49
50. lecture 2 the scientific method - earth’s motion Stars in this direction visible at night orbit of the earth 50
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69. lecture 2 the scientific method - earth’s motion visibility and latitude Stars in this direction visible from this latitude “horizon” “horizon” “zenith” North North equator 69
70. lecture 2 the scientific method - earth’s motion visibility and latitude 70
71. lecture 2 the scientific method - earth’s motion visibility and latitude 71
72. lecture 2 the scientific method - earth’s motion visibility and latitude 72
73. lecture 2 the scientific method - earth’s motion visibility and latitude 73
74. lecture 2 the scientific method - earth’s motion visibility and latitude 90o 74
75. lecture 2 the scientific method - earth’s motion 150 million km Perihelion 147.09 x 106 km Aphelion 152.10 x 106 km (only 3% difference!) orbit of the earth 75
76. lecture 2 the scientific method - earth’s motion Equator ecliptic angle = 23.4 deg angle between the orbital plane of the earth and equator orbit of the earth III. axis tilt 76
77. lecture 2 the scientific method - earth’s motion orbit of the earth NCP NeclipticP 23.4o SCP 77
78. lecture 2 the scientific method - earth’s motion orbit of the earth NCP NeclipticP SCP summer solstice winter solstice 23.4o 78
79. lecture 2 the scientific method - earth’s motion Summer Solstice Jun 20 Autumnal Equinox Sep 23 Winter Solstice Dec 21 H.A. = 0 @ midnight? Vernal Equinox March 21 79
80. lecture 2 the scientific method - earth’s motion RA = 18h RA = 0h RA = 6h Summer Solstice Jun 20 Autumnal Equinox Sep 23 Winter Solstice Dec 21 RA = 12h Vernal Equinox March 21 80
81. lecture 2 the scientific method - earth’s motion RA = 18h RA = 0h RA = 6h Summer Solstice Jun 20 Autumnal Equinox Sep 23 Winter Solstice Dec 21 RA = 12h Vernal Equinox March 21 81
82. lecture 2 the scientific method - earth’s motion RA = 18h RA = 0h RA = 6h Summer Solstice Jun 20 Autumnal Equinox Sep 23 Winter Solstice Dec 21 RA = 12h Vernal Equinox March 21 82
83. lecture 2 the scientific method - earth’s motion RA = 18h RA = 0h RA = 6h Summer Solstice Jun 20 Autumnal Equinox Sep 23 Winter Solstice Dec 21 RA = 12h Vernal Equinox March 21 83
84. lecture 2 the scientific method - earth’s motion seasons 84
85. lecture 2 the scientific method - earth’s motion seasons December 21 (southern hemisphere summer) 85
86. lecture 2 the scientific method - earth’s motion seasons June 21 (northern hemisphere summer) 86
87. lecture 2 the scientific method - earth’s motion seasons December 21 (northern hemisphere winter) 87
88. lecture 2 the scientific method - earth’s motion seasons December 21 (southern hemisphere summer) • earth is closer to the sun • solar cycles • changes in magnetic field of the earth 88
89. lecture 2 the scientific method - earth’s motion seasons December 21 (southern hemisphere summer) • earth is closer to the sun • solar cycles • changes in magnetic field of the earth • other 89
90. lecture 2 the scientific method - earth’s motion 150 million km Perihelion 147.09 x 106 km Aphelion 152.10 x 106 km (only 3% difference!) seasons 90
91. lecture 2 the scientific method - earth’s motion seasons December 21 (southern hemisphere summer) • sun radiation incident at a perpendicular angle • longer days: sun radiation integrated for longer time • less atmospheric dispersion 91
92. lecture 2 the scientific method - earth’s motion SUN equator NP 92
93. lecture 2 the scientific method - earth’s motion equator NP SUN winter solstice 93
94. lecture 2 the scientific method - earth’s motion equator NP SUN summer solstice 94
95. lecture 2 the scientific method - earth’s motion equator SUN equinox SP NP SP 95
96. lecture 2 the scientific method - earth’s motion equator tropic of cancer tropic of capricorn antarctic circle arctic circle what is the declination of the sun? SUN 96
97. lecture 2 the scientific method - earth’s motion equator what is the declination of the sun? tropic of cancer tropic of capricorn antarctic circle arctic circle RA Dec -90d 90d 24h 0h SUN ...homework... 97
98. lecture 2 the scientific method - earth’s motion but why all this rotation??? 98
99. lecture 2 the scientific method - earth’s motion Each star that forms has a disk of hydrogen and helium (and heavier elements) surrounding it. Within this disk, planets form. 99
100. lecture 2 the scientific method - earth’s motion Each star that forms has a disk of hydrogen and helium (and heavier elements) surrounding it. Within this disk, planets form. 100
101. lecture 2 the scientific method - earth’s motion Each star that forms has a disk of hydrogen and helium (and heavier elements) surrounding it. Within this disk, planets form. 101
102. lecture 2 the scientific method - earth’s motion Minor Planet Center: http://minorplanetcenter.net/ 102
103. lecture 1 overview - coordinates summary 1.The modern epistemological paradigm is based on falsifiability (and simplicity) 2. Celestial bodies are in continuous motion: the earth spins, revolves, the galaxy rotates, the local group moves ... 3.The Earth’s spin causes celestial bodies apparent daily motion 4. The hour circles moves 4 min/day due to the rotation of the Earth around the Sun changing the night sky landscape seasonally 5. The ecliptic is tilted 23.4o from the Earth’s equatorial plane 6. Seasons are due to reasons all connected to this mis-alignment 7. The rotation of the Solar System bodies is to be understood in the context of Solar System formation from collapse of a gas cloud 103
104. lecture 1 overview - coordinates reading Kaler Chapter 2-3 by next class. Many of the concepts we went through are developed in the course of Chapter 2, so you must have already done some of the work! Look up times: http://www.astronomy.ohio-state.edu/~pogge/Ast161/Unit2/ time.html Wikipedia is a good resource for the scientific method: start at http://en.wikipedia.org/wiki/Falsifiability and if you are interested follow the links, to Positivism, to Probabilistic or non-probabilistic induction, etc... Read the first outdoors lab: we may go out this week! 104
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